“Our system is killing our children”, claimed one teacher during a passionate debate about primary testing over the weekend.

“We must bring down this whole stinking edifice,” she told an audience of activists in Cardiff, who had earlier been rallied to “decapitate” the Sats “monster”.

This year’s Easter teaching union conferences had plenty of the usual fiery rhetoric. But in reality, it is increasingly rare for industrial action threats to be acted upon.

Will this year be any different? Does the government - today’s or any future administration - have anything to fear from teaching unions?

The answer could be affected by several developments, not least the plans to hold a 8 June general election, announced by Theresa May on Tuesday. There is also the looming September merger of the ATL and NUT teaching unions.

Summer strike

Observers might have expected ATL members to be a moderating influence on their new partners. But the leaders of both organisations have warned that their combined clout in the National Education Union will mean teachers “can no longer be ignored”.

This year would have been different anyway thanks to the government planning a national school funding formula just as schools are experiencing their tightest budgets for years.

The NUT voted last week to call a one-day strike over funding in the summer term, though only in certain regions.

“There would be nothing immoral about striking against these cuts,” NUT general secretary Kevin Courtney warned. He has pointed out that some of the biggest opponents to the current school funding squeeze have been “Conservative MPs with the highest majorities.”

But that was before we knew that the UK was about to head back to the polls. The danger for the teaching unions is that the general election could break the momentum that had been building against some of the government’s most controversial education policies. The Conservatives could go on to win and implement the planned changes with renewed vigour.

Neil Carmichael, the Conservative MP and chairman of the Commons Education Select Committee, has long been a proponent of modifying the current school funding formula. But he thinks that May’s decision to call a snap election next month will end up harming the teaching unions’ cause.

“The election will change the political weather to a certain extent,” he says. “That’s what they do.

“The Labour manifesto will be implausible in almost every respect. We will see how the electorate will respond to that. I think it will probably take the wind out of the sails of the [teaching] unions.”

Staging an effective national teachers’ strike would require securing the support of a broad majority of parents - and the foundations are already being laid.

“We’re seeing huge numbers of parental meetings,” Courtney says. “These are significant mobilisations of people who are shocked, outraged by what’s happening in their children’s schools.

“And that’s where our planning horizon is at the moment; how much can we build support from those at those parental meetings?”

That is why the union invited Jo Yurky, co-founder of Fair Funding for All Schools - a parent-led group that is campaigning against school funding cuts - to speak at this year’s NUT conference.

She believes that her group would back a teachers’ strike and sees school funding as approaching a “poll tax moment”.

“Many of the people taking part in our campaign are people who are completely new to this sort of thing - who haven’t gone to a public meeting in their lives, who have never stood on the street and handed out a leaflet before,” Yurky says. “That’s what makes it different.”

It is that combination of parents and teachers working together that could pose the greatest threat for the government.

Primary concerns

But funding is far from the only issue currently raising hackles - and heckles. Concerns over teacher workload and pay dominated the NASUWT teaching union conference. There was also immense anger over primary testing across all three of the main classroom unions.

At the start of conference season, ATL members voted overwhelmingly to “explore a possible boycott of all tests at primary level”. Whether this will actually go on to amount to anything is yet to be seen; a similar move was mooted by the ATL’s general secretary, Mary Bousted, last August. However, nothing came of it.

But on Tuesday Courtney warned that the NUT would “break” primary assessment if Sats reform did not materialise.

There is, however, no consensus across the profession about the right time to take action on any issue.

Although last week’s NASUWT conference in Manchester passed several motions calling for industrial action, there were also members who cautioned that negotiation and action short of strikes can be most effective.

Doubt was also cast during the debates over whether some areas of England, including the South East, would be prepared to go through with industrial action.

Patrick Roach, deputy general secretary of the NASUWT, says of his union’s approach: “This is not about trying to strike fear into the heart of government.”

The government “has to take seriously our ability to use industrial action if we need to”, he says. But “negotiation can get you a long way”, Roach adds.

Even if the profession can be persuaded to take co-ordinated industrial action, there are now further obstacles to overcome. The new 2016 Trade Union Act says unions in certain public services, including education, have to get 50 per cent of members to return their ballot papers and 40 per cent of all members to vote yes before national industrial action can take place.

Courtney acknowledges the huge challenge this presents, highlighting that the teacher pensions dispute in 2011 only attracted a 40 per cent turnout.

“But when members know that not voting is exactly the same as a no vote, then we think we could improve the turnout on that basis,” he says.

An independent review is due to recommend whether or not to allow electronic voting - which Courtney has previously suggested would help to get past the new turnout threshold. But the review may not issue its report until as late as December.